article: Trees are useful to man in three very important ways. The first important way is that they provide man with food, wood and other products. Trees provide not only man with food, but also many animals with food. Without trees many animals could not live on the earth. It's not easy for man to live on the earth, either.
  The second important way is that trees give us shade. On a hot summer day, people are eager to have a rest under the shade of a tree after they have walked a long way. You can imagine how important the shade of a tree is to man and to animals.
  The third important way is that trees help to prevent drought and floods . However, in many parts of the world, man has not realized the third important way. _ has cut trees down in large numbers. In the end he finds that he has lost the best friends he had.
question: Trees are important to man in  _  ways.
options: 2 3 4 5